Sample dispensing system for liquid chromatography

ABSTRACT

A method and apparatus for supplying a preset amount of sample solution to a liquid chromatographic column wherein (1) a first piston, which moves along the axis of a piston container sealingly contacting the side walls of said piston container, is moved a preset distance so as to draw a fixed amount of driving solution from the driving solution chamber of a piston cylinder into the piston container, thus displacing a second piston which moves along the axis of said piston cylinder sealingly contacting the side walls of said piston cylinder and dividing said piston cylinder into a sample solution chamber and a driving solution chamber, said displacement of said second piston serving to cause sample solution to be drawn from a sample solution reservoir into the sample solution chamber of the piston cylinder in a fixed amount equal to the fixed amount of driving solution drawn into the piston container; and (2) driving solution is pumped into said driving solution chamber in order to displace said second piston so that sample solution in the sample solution chamber is forced out of the sample solution chamber and onto said chromatographic column.

BACKGROUND OF THE INVENTION

The invention relates to an automated method and an apparatus forfilling a piston cylinder with a variable but preset amount of samplesolution and then discharging the sample solution from said pistoncylinder onto a liquid chromatographic column.

Liquid chromatography is a well known separation technique which isutilized for separating various components contained in a sample. In thepractice of liquid chromatography, it has been the custom to feed ameasured amount of a sample solution containing a mixture of componentsneeding to be separated to the top of a fractionation column of achromatography material, e.g. gel particles, and then a suitable mobilephase (driving solution) is allowed to pass through the column, bringingwith it components contained in the sample solution. The variouscomponents of the sample solution will, depending upon different degreesof interaction with the chromatography material, pass through the columnat different speeds, thereby making it possible to separate the variouscomponents of the sample from each other.

A prerequisite for obtaining optimal results in liquid chromatographicseparation is that the sample has to be applied on the column correctly.A common method of applying the sample solution onto the column is toapply the desired amount by means of an injection syringe. This manualmethod has obvious limitations.

Another prerequisite for obtaining optimal results in liquidchromatographic separation is that any appreciable intermixing of samplesolution with driving solution prior to fractionation of the samplesolution on the column should be avoided. If any appreciable intermixingof the sample solution with the driving solution occurs before actualfractionating of the sample solution on the column, such intermixingcauses the separation bands to be fuzzy or to result in "tailing".

One method and apparatus for applying a variable but preset amount ofsample solution to a chromatographic column is taught in U.S. Pat. No.4,389,316 which makes use of a sample container of uniformcross-section, which by means of a piston is divided into a drivingsolution chamber and a sample solution chamber. The piston is slideablein the tubular container while sealing against the container wall sothat the two chambers normally do not communicate with each other.Sample solution may be drawn into the sample solution chamber by movingthe piston upwards in said sample container via a control handleattached to the piston rod which is attached to the piston. Said samplecontainer may be marked with gradations so that the piston can be moveda preset amount in order to permit a fixed amount of sample solution toenter the sample solution chamber. Driving solution is then pumped intothe driving solution chamber and this displaces the piston, thusdischarging said fixed amount of sample solution to the chromatographiccolumn. A few disadvantages to this method and apparatus are (1)difficulty of automation; (2) inability to vary the preset fixed amountof sample solution by small increments; (3) difficulty of providing ahigh pressure (e.g. 2000 psi) sliding seal to the outside, etc.

It is therefore an object of the invention to provide an automatedmethod and apparatus for supplying a preset amount of sample solution toa liquid chromatographic column.

It is a further object of the invention to provide such a method andapparatus in which the preset amount of sample solution can be varied bysmall increments.

It is still a further object of the invention to provide such a methodand apparatus in which any appreciable intermixing of sample solutionwith driving solution prior to fractionation of the sample solution onthe column is avoided.

These and other advantages are obtained in accordance with the inventionby means of the method and the apparatus for sample application definedin the following claims and described in more detail below.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic view of one embodiment of the apparatus of theinvention.

FIG. 2 a, b, c, d, e and f are schematic diagrams illustrating oneembodiment of the sample application method according to the invention.

FIG. 3 illustrates a portion of one embodiment of a pneumatic system ofthe invention.

FIG. 4 illustrates one embodiment of the piston which divides the pistoncylinder into a sample solution chamber and a driving solution chamber.

FIG. 5 is an enlarged view of the portion of the piston of FIG. 4 withthe flexible sliding seal.

FIG. 6 is a sectional view taken along line 1--1 of FIG. 4 of the legsof said piston.

SUMMARY OF THE INVENTION

The objects of the invention are accomplished by a method and apparatusfor supplying a preset but variable amount of sample solution to aliquid chromatographic column in which (1) a first piston, which movesalong the axis of a piston container sealingly contacting the side wallsof said piston container, is moved a preset distance so as to draw afixed amount of driving solution from the driving solution chamber of apiston cylinder into the piston container, thus displacing a secondpiston which moves along the axis of said piston cylinder sealinglycontacting the side walls of said piston cylinder and dividing saidpiston cylinder into a sample solution chamber and a driving solutionchamber, said piston cylinder having a sample solution chamber end and adriving solution chamber end, said displacement of said second pistonserving to cause sample solution to be drawn from a sample solutionreservoir into the sample solution chamber of the piston cylinder in afixed amount equal to the fixed amount of driving solution drawn intothe piston container and (2) driving solution is pumped into saiddriving solution chamber in order to displace said second piston so thatsample solution in the sample solution chamber is forced out of thesample solution chamber and onto said chromatographic column. Prior topumping driving solution into said driving solution chamber, therepreferably is a further step of moving the first piston back to itsinitial position, the driving solution in said piston container beingexpelled to waste. The steps of moving the first piston a presetdistance and then moving the first piston back to its initial positionas described above, are repeated in sequence as many times as necessaryuntil the desired amount of sample solution to be loaded onto thechromatographic column is obtained in the sample solution chamber.

In order to be able to vary the preset amount of sample solution bysmall increments, the diameter of the piston container is preferablyless than the diameter of the piston cylinder and more preferably isless than or equal to half the diameter of the piston cylinder.Preferably, the volume capacity of the piston container is less than thevolume capacity of the piston cylinder. The means for moving the firstpiston preferably comprises a pneumatic system, since a pneumatic systemwould be explosionproof. The second piston preferably comprises a freelymovable piston and there preferably are stop means, either attached tosaid second piston or to said sample solution chamber end of the pistoncylinder, which prevent said second piston from contacting the samplesolution chamber end of the piston cylinder. Furthermore, therepreferably is a flexible sliding seal around the second piston thatenables said second piston to sealingly contact the side walls of saidpiston cylinder and which sliding seal bends under pressure to allowdriving solution from the driving solution chamber to enter the samplesolution chamber when said stop means attached to said second pistoncontacts the sample solution chamber end of the piston cylinder or whenthe second piston contacts the stop means attached to the samplesolution chamber end of the piston cylinder.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIGS. 1,2, and 3, piston container 2, having uniform crosssection, is provided with piston 4 which is adapted to move along theaxis of piston container 2 sealingly contacting the side walls of pistoncontainer 2. One way of forming said sliding seal, as shown in FIG. 3,would be to use an O-ring 5 around piston 4. Another way of forming saidsliding seal would be to machine piston 4 in such a way that there wouldbe a tight fit between piston 4 and piston container 2. Piston 4 isconnected to a piston rod 6. Piston container 2 is preferably acommercial glass syringe with a Teflon® (polytetrafluoroethylenematerial obtained from E. 1. duPont de Nemours & Co.) plunger in whichthe sliding seal is formed by a tight fit. Piston container 2 has apassageway 8 at one end of the introduction and removal of drivingsolution, the other end of piston container 2 being open to theatmosphere.

What is meant here by container is a structure that has side walls andtwo ends, one end of which is open to the atmosphere. This is to bedistinguished from cylinder which refers to a structure that has sidewalls and two ends, neither end of which is open to the atmosphere.

Piston cylinder 10, having uniform cross section, is provided with afreely movable piston 12 which is adapted to move along the axis ofpiston cylinder 10 sealingly contacting the side walls of pistoncylinder 10 and dividing said piston cylinder into a sample solutionchamber 20 and a driving solution chamber 22, said piston cylinder 10having two ends, a sample solution chamber end 26 and a driving solutionchamber end 28. When pressure is applied to either the sample solutionchamber 20 or the driving solution chamber 22, piston 12 moves freely inthe direction of the pressure. As seen more clearly in FIGS. 4 and 5,piston 12 is formed from a piston face 14 and piston body 16 which areattached together with a seal 18, formed of a flexible material (such asrubber or Kalrez ®--obtained from E. I. duPont de Nemours & Co.),sandwiched between. The seal 18 is of such a dimension as to rub againstpiston cylinder 10 and normally serves to prevent intermixing betweenliquid in the sample solution chamber 20 and driving solution chamber22. Nubs 24 are attached to said piston face 14 to prevent piston 12from contacting the sample solution chamber end 26 of piston cylinder10. Instead of having nubs 24 attached to the piston face 14, nubs couldbe attached to the sample solution chamber end 26 of the piston cylinder10 to prevent piston 12 from contacting the sample solution chamber end26 of piston cylinder 10. At least one nub, but preferably more, ispreferably attached either to piston 12 or to sample solution chamberend 26 to prevent piston 12 from contacting the sample solution chamberend 26 of piston cylinder 10. When the piston 12 reaches the samplesolution chamber end 26, the nubs 24 prevent direct contact betweenpiston 12 and the sample solution chamber end 26, but prevent piston 12from making any further movement. The high pressure drop that thusdevelops across the seal 18 forces the flexible seal 18 to bend, asshown in FIG. 5, thus opening a space between the seal 18 and the sidewalls of piston cylinder 10 and allowing driving solution from thedriving solution chamber 22 to enter the sample solution chamber 22. Asseen in FIG. 6, the piston body 16 has four legs 30 to allow free flowof liquid around the piston body 16, but maintain proper alignment ofthe piston 12 in the piston cylinder 10. Sample solution chamber 20 hasa passageway 32 for the introduction and removal of sample solution anddriving solution chamber 22 has a passageway 34 for the introduction andremoval of driving solution.

An adjustable valve 36, which is preferably a 2 position 6 port valve asshown in FIG. 1, is adjustable between a sample application position andan elution position. The broken connection lines in the valve 36 in FIG.1 mark the sample application position, whereas the unbroken (solid)connection lines mark the elution position. The adjustment of valve 36between the two positions can be made manually, but is preferablyperformed by a control unit which automatically resets the valve 36. Apump 38 for pumping driving solution from a driving solution reservoir40 into driving solution chamber 22 and for pumping driving solutionfrom driving solution reservoir 40 onto chromatographic column 42 isconnected to port 44 of said valve 36 via conduit 46. Passageway 34 ofdriving solution chamber 22 is connected to port 48 of valve 36 viaconduit 50. Passageway 8 of piston container 2 is connected to port 52of valve 36 via conduit 54. A sample solution reservoir 56 is connectedto port 58 of valve 36 via conduit 60. Passageway 32 of sample solutionchamber 20 is connected to port 62 of value 36 via conduit 64.Chromatographic column 42 is connected to port 66 of valve 36 viaconduit 68. Thus, valve 36 serves to interconnect pump 38 with drivingsolution chamber 22, driving solution chamber 22 with piston container2, piston container 2 with sample solution reservoir 56, sample solutionreservoir 56 with sample solution chamber 20, sample solution chamber 20with chromatographic column 42 and chromatographic column 42 with pump38. In the elution application position shown in unbroken connectionlines in FIG. 1, the pump 38 pumps driving solution to thechromatographic column 42, and by moving piston 4 down a presetdistance, a fixed amount of driving solution is drawn from drivingsolution chamber 22 into piston container 2, thus displacing piston 12downward, the displacement of piston 12 downward serving to draw samplesolution from the sample solution reservoir 56, in a fixed amount equalto the fixed amount of driving solution drawn into piston container 2,into the sample solution chamber 20. In the sample application positionshown in broken connection lines in FIG. 1, the pump 38 pumps drivingsolution to driving solution chamber 22 which displaces piston 12upwards, thus serving to force sample solution in the sample solutionchamber 20 (or driving solution which has entered the sample solutionchamber 20 as a result of the bending of flexible scal 18 due topressure) onto chromatographic column 42.

If it is desired to load more sample solution onto the chromatographiccolumn 42 than that obtained in sample solution chamber 20 by virtue ofmoving piston 2 down a preset distance once, then a waste container ofany form 70 is connected to piston container 2. One way of connectingwaste container 70 to piston container 2 would be via conduit 72, whichconduit 72 could be connected to conduit 54, as shown in FIG. 1, by somemeans such as a T joint, thus passageway 8 of piston container 2 wouldbe connected to waste container 70 via conduit 54 and conduit 72. Ifpiston container 2 was connected to waste container 70 via a conduit,then it would be necessary for said conduit, conduit 72 in FIG. 1, tohave a check valve 74 (check valve by definition only allows flow in onedirection) to ensure that solution cannot flow from waste container 70to piston container 2 and there would need to be a check valve, such ascheck valve means 76 on conduit 60, to ensure that driving solution frompiston container 2 only flows to the waste container. Although thislatter check valve could have been located, for example, on conduit 54above the juncture of conduits 54 and 72, by having check valve 76located on conduit 60, it serves a dual function of ensuring thatdriving solution from piston container 2 only flows into waste container70 and that driving solution cannot flow into sample solution reservoir56 when valve 36 is reset to the eluent position. Another way ofconnecting waste container 70 to piston container 2 (not shown) would beto have a valve, e.g. a 3 way valve, on conduit 54 connected to thewaste container via a conduit and a controlling means to control theopening and closing of the valve ports of said valve.

The system illustrated in FIGS. 1 and 2, can according to the inventionbe used in the following way. First, the driving solution chamber 22 ofthe piston cylinder 10 is filled with driving solution, e.g. a buffersolution or other type of solution depending on the nature of the samplesolution. This can be done as shown in FIG. 2a by setting valve 36 tothe sample application position so that pump 38 can pump drivingsolution from driving solution reservoir 40 to driving solution chamber22. By pumping driving solution into driving solution chamber 22, piston12 is moved upward. As described previously, when piston 12 has beenmoved upward enough that nubs 24 on piston 12 contact the samplesolution chamber end 26, the flexible seal 18 bends and driving solutionfrom the driving solution chamber 22 enters the sample solution chamber22 and can go from there into conduit 64, conduit 68 and chromatographiccolumn 42.

After the driving solution chamber 22 of piston cylinder 10 is filledwith driving solution, driving solution is preferably pumped intochromatographic column 42 in order to equilibrate column 42. This can bedone, as seen in FIG. 2b, by setting valve 36 to its second position,the eluent position, and using pump 38 to pump driving solution fromdriving solution reservoir 40 directly to column 42.

Next, with valve 36 in the eluent position as seen in FIG. 2c, piston 4is moved downward from the top of piston container 2 a preset amount inpiston container 2, creating suction so that a fixed amount of drivingsolution is drawn from driving solution chamber 22 into piston container2 through passageway 8. The reduced pressure in conduit 72 caused by themovement down of piston 4 serves to close check valve 74 more tightly.This decrease in the amount of driving solution in driving solutionchamber 22 causes freely movable piston 12 to be displaced downward,creating suction so that check valve 76 opens and sample solution fromsample solution reservoir 56 is drawn into sample solution chamber 20 ina fixed amount equal to the fixed amount of driving solution drawn intopiston container 2. As seen in FIG. 2c, while the sample solution isbeing drawn into sample solution chamber 20, pump 38 can be pumpingdriving solution from driving solution reservoir 40 to chromatographiccolumn 42.

If no more sample solution, other than the sample solution obtained insample solution chamber 20 as a result of moving piston 4 down a presetdistance once, is desired to be loaded on chromatographic column 42,then valve 36 is set to its sample application position, as seen in FIG.2e and pump 38 pumps driving solution from driving solution reservoir 40into driving solution chamber 22, thus displacing piston 12 upwards andserving to discharge sample solution from sample solution chamber 20onto chromatographic column 42.

However, if more sample solution than the sample solution obtained insample solution chamber 20 as a result of moving piston 4 down a presetdistance once is desired to be loaded on chromatographic column 42, thenwith valve 36 in the eluent position, piston 4 is moved upward to itsinitial position as seen in FIG. 2d. This movement of piston 4 upwardscauses an increase in pressure in conduits 54, 50, 64 and 70, thusserving to close check valve 76 more tightly and to open check valve 74so that driving solution from piston container 2 is discharged intowaste container 70. The above-described steps of moving piston 4 down apreset amount in order to obtain a fixed amount of sample solution insample solution chamber 20 and moving piston 4 back up to its initialposition at the top of piston container 2 in order to expel drivingsolution in piston container 2 to waste are repeated in sequence as manytimes as necessary until the desired amount of sample solution to beloaded onto chromatographic column 42 is obtained in sample solutionchamber 20.

After the desired amount of sample solution to be loaded onto column 42is obtained in sample solution chamber 20, then as above-discussed,valve 36 is set to its sample application position, as seen in FIG. 2e,and pump 38 pumps driving solution from driving solution reservoir 40into driving solution chamber 22, thus displacing piston 12 upwards andserving to discharge sample solution from sample solution chamber 20onto column 42. As seen in FIG. 2f, once piston 12 has been moved upwardenough that nubs 24 on piston 12 contact the sample solution chamber end26, the flexible seal 18 bends and driving solution from drivingsolution chamber 22 enters the sample solution chamber 20 and forces anyremaining sample solution in sample solution chamber 20 onto the column42.

Once all the sample solution in sample solution chamber 20 has beendischarged onto chromatographic column 42, the supply of drivingsolution to the driving solution chamber 22 is interrupted, e.g. bysetting valve 36 to its eluent position, and driving solution is thenpumped directly to the chromatographic column in order to elute samplecomponents from the column, e.g. by pumping driving solution fromdriving solution reservoir 40 directly to chromatographic column 42.

Although any means for moving piston 4 a present amount in pistoncontainer 2 will do, the means for moving piston 4 in piston container 2preferably comprises a pneumatic system. As seen in FIGS. 1,2 and 3, thepneumatic system preferably comprises an air cylinder 76, having uniformcross section, which is provided with piston 78, piston 78 being adaptedto move along the axis of air cylinder 76 sealingly contacting the sidewalls of air cylinder 76 and dividing air cylinder 76 into chamber 79and chamber 80. One way of forming said sliding seal, as seen in FIG. 3,would be to use an O-ring 81 around piston 78. Piston 78 is connected topiston 4 through the open end of piston container 2. As seen in FIGS.1,2 and 3, the preferred way to connect piston 78 to piston 4 is toconnect piston rod 82, which is connected at one end to piston 78, to alever arm 84 at the other end of piston rod 82 and to connect piston rod6, which is connected at one end to piston 4, to lever arm 84 at theother end of piston rod 6. Lever arm 84 has a pivot 86 preferablylocated at one end of the lever arm 84 which allows lever arm 84 topivot.

Said preferable pneumatic system further comprises passageway 88 for theintroduction of air to chamber 79 of air cylinder 76; passageway 90 forthe introduction of air to chamber 80 of air cylinder 76; a means forsupplying air into cylinder 76 through passageways 88 and 90; and acontrolling means 92 for controlling the supply of air to passageways 88and 90. One suitable means for supplying air into air cylinder 76through passageways 88 and 90 comprises air pumping means 93 and a valve94 which interconnects air pumping means 93 to passageways 88 and 90.Valve 94 is preferably a four port valve with passageway 88 beingconnected to one port via conduit 96, air pumping means 93 beingconnected to a second port via conduit 98, passageway 90 being connectedto a third port via conduit 100 and the fourth port being connected tothe atmosphere (thus allowing for air passing through valve 94 to bevented to the atmosphere) via conduit 102. Controlling means 92 thuscontrols the supply of air to passageways 88 and 90 by controlling theopening and closing of the valve ports of valve 94.

The means for presetting the amount that piston 4 will move in pistoncontainer 2 preferably comprises a lever arm stop means 104 locatedadjacent to lever arm 84, said lever arm stop means 104 having lever armstops 106 and said lever arm stop means 104 preferably being locatedadjacent to the end of lever arm 84 opposite to the end of lever arm 84on which pivot 86 is located.

When air is pumped through conduit 96 to passageway 88, piston 78 isdriven downward, thus driving piston rod 82 downward which causes thelever arm 84 to be pushed downward around the pivot 86. This movement oflever arm 84 downward in turn pulls piston rod 6 and thus piston 4downward drawing driving solution from driving solution chamber 22 intothe space formed above piston 4. This continues until the lever arm 84hits the lever arm stop 106, which lever arm stop is preset to determinethe movement of the lever arm 84 and thus the volume of driving solutiondrawn into piston container 2. When air is pumped through conduit 100 topassageway 90, piston 78 is driven upward, thus driving piston rod 82upward which causes lever arm 84 to be pushed upward. This movement oflever arm 84 upward in turn pulls piston rod 6 and thus piston 4 upward,thus discharging driving solution from piston container 2. Thiscontinues until the lever arm 84 hits the other lever arm stop 106.

As seen in FIG. 2, the controlling means 92 preferably has a counter 108that is set so that piston 4 is lowered and raised a preset distance acertain amount of times based on the supply of air to passageways 88 and90.

The parts of the apparatus of this invention that are to be wetted withdriving solution or sample solution are preferably made out of amaterial that is compatible with a wide range of driving and samplesolutions, e.g., stainless steel, Teflon®, glass, Kalrez®, etc.

As beforementioned, in order to be able to vary the preset amount ofsample solution by small increments, the diameter of the pistoncontainer 2 is preferably less than the diameter of the piston cylinder10, more preferably is less than or equal to half the diameter of thepiston cylinder 10, and most preferably is less than or equal toone-third the diameter of piston cylinder 10. The volume capacity ofpiston container 2 is also preferably less than the volume capacity ofpiston cylinder 10. In fact, piston container 2 is preferably acommercial syringe with a plunger, with the maximum volume capacityranging from 50 microliters to 50 milliliters and more preferably from 1to 10 milliliters.

Although this invention has been described with reference to itspreferred embodiment, other embodiments can achieve the same results.Variations and modifications to the present invention will be obvious tothose skilled in the art and it is intended to cover in the appendedclaims all such modifications and equivalents that follow in the truespirit and scope of this invention.

We claim:
 1. A system for applying a sample solution to a liquidchromatographic column comprising:(a) a piston container; (b) a firstpiston adapted to move along the axis of said piston container sealinglycontacting the side walls of said piston container; (c) a firstpassageway for the introduction and removal of driving solution to andfrom said piston container; (d) means for moving said first piston insaid piston container; (e) means for presetting the amount that saidfirst piston will move in said piston container; (f) a piston cylinder;(g) a second piston adapted to move along the axis of said pistoncylinder sealingly contacting the side walls of said piston cylinder anddividing said piston cylinder into a sample solution chamber and adriving solution chamber, said piston cylinder having two ends, a samplesolution chamber end and a driving solution chamber end; (h) a secondpassageway for the introduction and removal of sample solution to andfrom said sample solution chamber; (i) a third passageway for theintroduction and removal of driving solution to and from said drivingsolution chamber; (j) a driving solution reservoir; (k) a samplesolution reservoir; (l) a chromatographic column; (m) pumping means forpumping driving solution from said driving solution reservoir into saiddriving solution chamber through said third passageway and for pumping adriving solution from said driving solution reservoir onto saidchromatographic column; (n) a first valve means (A) interconnecting saidpumping means with said driving solution chamber; (B) interconnectingsaid driving solution chamber with said piston container; (C)interconnecting said piston container with said sample solutionreservoir; (D) interconnecting said sample solution reservoir with saidsample solution chamber; (E) interconnecting said sample solutionchamber with said chromatographic column; and (F) interconnecting saidchromatographic column with said pumping means, wherein said pumpingmeans is connected to said first valve means via a first conduit; saidthird passageway of said driving solution chamber is connected to saidfirst valve means via a second conduit; said first passageway of saidpiston container is connected to said first valve means via a thirdconduit; said second passageway of said sample solution chamber isconnected to said first valve means via a fourth conduit; said samplesolution reservoir is connected to said first valve means via a fifthconduit; and said chromatographic column is connected to said firstvalve means via a sixth conduit.
 2. The system of claim 1 furthercomprising:a waste container; and means for connecting said wastecontainer to said piston container.
 3. The system of claim 2 whereinsaid fifth conduit has a first check valve means which ensures thatsolution cannot flow into said sample solution reservoir and said meansfor connecting said piston container to said waste container comprises aseventh conduit, said seventh conduit having a second check valve meanswhich ensures that solution cannot flow from said waste container tosaid piston container.
 4. The system of claim 3 wherein the seventhconduit is connected to the third conduit and wherein the firstpassageway of said piston container is connected to said waste containervia said third and seventh conduits.
 5. The system of claim 2 whereinsaid means for connecting said piston container to said waste containercomprises:a second valve means on said third conduit, said second valvemeans having valve ports and said second valve means being connected tosaid waste container via an eighth conduit; and a first controllingmeans to control the opening and closing of the valve ports of saidsecond valve means.
 6. The system of claim 1 wherein the diameter ofsaid piston container is equal to or less than half the diameter of saidpiston cylinder.
 7. The system of claim 1 wherein the means for movingsaid first pistion comprises a pneumatic system.
 8. The system of claim7 wherein the piston container has two ends, one end containing thefirst passageway for the introduction and removal of driving solution toand from the piston container and the second end being open to theatmosphere, wherein the pneumatic system comprises:an air cylinder; athird piston adapted to move along the axis of said air cylindersealingly contacting the side walls of said air cylinder and dividingsaid air cylinder into a first chamber and a second chamber; means toconnect said third piston to said first piston through said open end ofsaid piston container; a fourth passageway for the introduction of airto said first chamber of said air cylinder; a fifth passageway for theintroduction of air to said second chamber of said air cylinder; meansfor supplying air into said air cylinder through said fourth and fifthpassageways; and a second controlling means to control the supply of airto the fourth and fifth passageways.
 9. The system of claim 8 whereinsaid means for supplying air into said air cylinder comprises:airpumping means; and a third valve means having valve ports, said thirdvalve means (A) interconnecting said air pumping means with said fourthpassageway; and (B) interconnecting said air pumping means with saidfifth passageway, wherein said third valve means is connected to the airpumping means via a first pneumatic conduit, said third valve means isconnected to the fourth passageway in the air cylinder via a secondpneumatic conduit, said third valve means is connected to the fifthpassageway in the air cylinder via a third pneumatic conduit, and afourth pneumatic conduit connects said third valve means to theatmosphere, thus allowing for air passing through said third valve meansto be vented to the atmosphere;and said second controlling meanscontrols the supply of air to the fourth and fifth passageways bycontrolling the opening and closing of the valve ports of the thirdvalve means.
 10. The system of claim 8 wherein the means to connect saidthird piston to said first piston through said open end of said pistoncontainer comprises:a first pistion rod having two ends, one end beingconnected to said first piston; a second piston rod having two ends, oneend being connected to said third piston; and a lever arm connected tosaid first and second piston rods at the ends of said first and secondpiston rods not connected to said first and second pistons, said leverarm having means to allow it to pivot;
 11. The system of claim 10wherein the means for presetting the amount that said first piston willmove in said piston container comprises a lever arm stop means locatedadjacent to said lever arm.
 12. The system of claim 10 wherein saidlever arm has two ends and said means to allow the lever arm to pivot islocated at one end of said lever arm.
 13. The system of claim 11 whereinthe means for presetting the amount that said first piston will move insaid piston container comprises a lever arm stop means located adjacentto the end of said lever arm opposite to the end of said lever arm thathas means to allow it to pivot.
 14. The system of claim 1 furthercomprising stop means to prevent said second piston from contacting thesample solution chamber end of the piston cylinder.
 15. The system ofclaim 14 wherein said stop means comprises at least one nub attached tosaid second piston.
 16. The system of claim 15 wherein there is aflexible sliding seal around the second piston that enables said secondpiston to sealingly contact the side walls of said piston cylinder andwhich sliding seal bends under pressure to allow driving solution fromthe driving solution chamber to enter the sample solution chamber whenthe stop means attached to said second piston contacts the samplesolution chamber end of the piston cylinder.
 17. The system of claim 14wherein said stop means comprises at least one nub attached to thesample solution chamber end of the piston cylinder.
 18. The system ofclaim 17 wherein there is a flexible sliding seal around the secondpiston that enables said second piston to sealingly contact the sidewalls of said piston cylinder and which sliding seal bends underpressure to allow driving solution from the driving solution chamber toenter the sample solution chamber when the second piston contacts thestop means attached to the sample solution chamber end of the pistoncylinder.